JPH0119593Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a DC power supply circuit.

Conventionally used DC power supplies generally supply a constant DC voltage while being supplied with power from an AC power supply. However, with this type of system, for example, if you want to energize a load such as a fan for a certain period of time after turning off the power switch, or if you want to turn on a warning lamp or sound a buzzer for a certain period of time, However, in addition to the above-mentioned DC power supply, the load must be operated using a relatively complicated circuit such as an electronic timer, which has the disadvantage that the power supply circuit and device become complicated and the cost increases.

The present invention is designed to eliminate the above drawbacks.
A switch circuit is provided with a capacitor that charges and discharges the power supplied from the AC power supply by turning the power switch on and off, and a transistor that turns on and off when the power switch is turned on and off. The present invention aims to provide a DC power supply circuit which drives a CR timer circuit with the discharge current of the capacitor after the supply is stopped, thereby supplying a constant DC voltage for a certain period of time.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a circuit diagram of the DC power supply of the present invention.
A rectifying and smoothing circuit consisting of a rectifying diode D1, a power drop resistor R1, and a smoothing capacitor C1 is connected to the power supply switch SW, and a power supply capacitor C2 is connected to the circuit through a backflow prevention diode D2. and the base of the transistor T1 of the first switch circuit are connected via an overvoltage prevention resistor R2. Further, the power supply capacitor C2 includes a resistor R3 and a capacitor C3.
A CR time constant circuit and a CR timer circuit including a transistor T2 are connected to a second switch circuit including transistors T3 and T4, and a load L is connected to the transistor T4 of the second switch circuit. Further, the collector of the transistor T1 of the first switch circuit is connected to the connection point between the resistor R3 and the capacitor C3 of the CR timer circuit and the base of the transistor T4 of the second switch circuit, respectively, through reverse current prevention diodes D3 and D4. , the base of a transistor T3 is connected to the collector of the transistor T2 of the CR timer circuit, and the base of a transistor T4 is connected to the collector of the transistor T3 of the second switch circuit. Resistance R
4, R5, and R6 are bias resistors, respectively.
ZD is a Zener diode for constant voltage effect connected to the base of transistor T4.

Therefore, as shown in the time chart in Figure 2, when the switch SW is on and power is supplied,
The power supply capacitor C2 is charged, but at this time the transistor T1 of the first switch circuit is turned on, so the resistor R3 of the CR timer circuit is grounded by the diode D3, so the capacitor C3 is not charged, and the diode D4 As a result, the base of the transistor T4 of the second switch circuit is grounded and turned off, so that no DC voltage is supplied to the load and it remains off. Then, when the power switch 2 is turned off at point A, the supply of AC power is stopped, and as a result, the transistor T1 of the first switch circuit is turned off.
is turned off, and the power supply capacitor C2 starts discharging, and the capacitor C3 of the CR timer circuit is gradually charged by a time constant. When the bias voltage of the transistor T2 is exceeded, the transistor T2 is turned on and the timer circuit outputs the voltage. The transistor T3 of the two-switch circuit is turned on, but during the period in which the capacitor C3 of this CR timer circuit is charged and the transistor T2 remains off, in Fig. 2 t,
When the transistor T4 of the second switch circuit is turned on, a constant DC voltage is applied to the load together with the Zener diode ZD, and when the transistor T3 is turned on due to time-up, the base of the transistor T4 is grounded and turned off, stopping the load. be.

As described above, with the present invention, whereas conventional DC power supplies output DC voltage while the power switch is on, the DC voltage is output by discharging the power supply capacitor after the power switch is turned off. Since this is a DC power supply circuit that drives a timer circuit and outputs a constant DC voltage for a certain period of time, it is suitable as a power source when you want to energize a load for a certain period of time after the power is turned off. It is possible to provide an extremely simple circuit at a low cost compared to conventional circuits that use complicated circuits. Further, since the circuit is simplified, it can be manufactured in a small size, and it is possible to provide a DC power supply circuit that is easy to handle and has excellent versatility.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an electric circuit diagram, and FIG. 2 is a time chart. E...AC power supply, SW...power switch, L...
...Load, T1-T4...Transistor, D1-D
4...Diode, R1~R6...Resistance, C1~
C3... Capacitor, ZD... Zener diode.

Claims (1)

[Scope of utility model registration request] A first switch circuit consisting of a power supply capacitor that charges and discharges when the power switch is turned on and off, a transistor that turns on and off when the power switch is turned on and off, and a CR timer that starts when the first switch circuit turns off. a circuit, and the first
a second switch circuit including a transistor that is turned on when the switch circuit is turned off and turned off by the output of the timer circuit;
A DC power supply circuit characterized in that the CR timer circuit and the second switch circuit are driven by the discharge of a power supply capacitor.